全文获取类型
收费全文 | 273472篇 |
免费 | 3635篇 |
国内免费 | 841篇 |
专业分类
化学 | 141632篇 |
晶体学 | 4219篇 |
力学 | 11442篇 |
综合类 | 2篇 |
数学 | 33754篇 |
物理学 | 86899篇 |
出版年
2021年 | 2050篇 |
2020年 | 2414篇 |
2019年 | 2643篇 |
2018年 | 3565篇 |
2017年 | 3442篇 |
2016年 | 5418篇 |
2015年 | 3623篇 |
2014年 | 5180篇 |
2013年 | 12751篇 |
2012年 | 10070篇 |
2011年 | 11815篇 |
2010年 | 8289篇 |
2009年 | 8043篇 |
2008年 | 10792篇 |
2007年 | 10635篇 |
2006年 | 9988篇 |
2005年 | 9268篇 |
2004年 | 8391篇 |
2003年 | 7373篇 |
2002年 | 7135篇 |
2001年 | 7883篇 |
2000年 | 6163篇 |
1999年 | 4780篇 |
1998年 | 4005篇 |
1997年 | 3822篇 |
1996年 | 3800篇 |
1995年 | 3379篇 |
1994年 | 3384篇 |
1993年 | 3432篇 |
1992年 | 3558篇 |
1991年 | 3677篇 |
1990年 | 3470篇 |
1989年 | 3329篇 |
1988年 | 3376篇 |
1987年 | 3224篇 |
1986年 | 3071篇 |
1985年 | 4173篇 |
1984年 | 4349篇 |
1983年 | 3487篇 |
1982年 | 3694篇 |
1981年 | 3620篇 |
1980年 | 3463篇 |
1979年 | 3563篇 |
1978年 | 3659篇 |
1977年 | 3579篇 |
1976年 | 3681篇 |
1975年 | 3346篇 |
1974年 | 3363篇 |
1973年 | 3424篇 |
1972年 | 2366篇 |
排序方式: 共有10000条查询结果,搜索用时 218 毫秒
971.
I. P. Raevskii L. A. Reznichenko M. P. Ivliev V. G. Smotrakov V. V. Eremkin M. A. Malitskaya L. A. Shilkina S. I. Shevtsova A. V. Borodin 《Crystallography Reports》2003,48(3):486-490
(Na, K)NbO3 crystals with a perovskite structure and a KNbO3 content up to 40 mol % were grown from flux with the use of the solvent NaBO2. The dielectric measurements of the crystals grown revealed phase transitions that had never been observed before in ceramic samples. 相似文献
972.
P. Q. Khanh 《Journal of Optimization Theory and Applications》1995,87(2):359-378
We prove the Kuhn-Tucker sufficient optimality condition, the Wolfe duality, and a modified Mond-Weir duality for vector optimization problems involving various types of invex-convexlike functions. The class of such functins contains many known generalized convex functions. As applications, we demonstrate that, under invex-convexlikeness assumptions, the Pontryagin maximum principle is a sufficient optimality condition for cooperative differential games. The Wolfe duality is established for these games.The author is indebted to the referees and Professor W. Stadler for valuable remarks and comments, which have been used to revise considerably the paper. 相似文献
973.
974.
S. Marinetti D. Robba F. Cernuschi P.G. Bison E. Grinzato 《Infrared Physics & Technology》2007,49(3):281-285
When performing in-field tests on thermal barrier coatings (TBCs) deposited on gas turbine blades, the main problem encountered is the difficulty to correctly interpret the experimental data. The coating thickness changes, which are not regarded as anomalies, are one of the most common sources of false alarms. They are very challenging to recognize because, unlike stains, eroded areas and optical property variations, they are not detectable in the visible band. Furthermore, their thermal signal is similar to the one produced by an adhesion defect. In this paper, a procedure to reliably discriminate thickness changes and real defects is proposed. The approach is based on the analysis of the apparent effusivity profile. Preliminary results are presented and discussed. 相似文献
975.
B. Sun Yu. A. Litvinov P. M. Walker K. Beckert P. Beller F. Bosch D. Boutin C. Brandau L. Chen C. Dimopoulou H. Geissel R. Knöbel C. Kozhuharov J. Kurcewicz S. A. Litvinov M. Mazzocco J. Meng C. Nociforo F. Nolden W. R. Plass C. Scheidenberger M. Steck H. Weick M. Winkler 《The European Physical Journal A - Hadrons and Nuclei》2007,31(3):393-394
A new long-lived isomeric state in the near proton dripline nucleus 125Ce has been identified with Schottky mass spectrometry at GSI. The excitation energy E
* = 103(12)keV and the decay time of 193(1)s have been obtained from a single stored fully ionized 125m
Ce58+ ion. The data implies an E3 transition and a 1/2+ assignment for the spin of the isomer. 相似文献
976.
977.
978.
The paper presents an exact analysis of the dispersion of an immiscible solute in a non-Newtonian fluid (known as an incompressible second-order fluid which shows viscoelastic behaviour) flowing slowly in a parallel plate channel in the presence of a periodic pressure gradient. Using a generalized dispersion model which is valid for all times after the solute injection, the diffusion coefficients K i (τ)(i=1,2,3,…) are obtained as functions of time τ in the case when the initial solute distribution is in the form of a slug of finite extent. The analysis leads to the novel result that K 2(τ) (which is a measure of the longitudinal dispersion coefficient of the solute) has a steady part S in addition to a fluctuating part D 2(τ) due to the pulsatility of the flow. It is found that S decreases with increase in the viscoelastic parameter M for given values of the amplitude λ and frequency ω of the pressure pulsation. On the other hand, it is found that at a fixed instant τ, the amplitude of D 2(τ) increases with increase in M for given values of λ and ω. Further it is shown that at a given instant τ, the amplitude of D 2(τ) decreases with increase in ω for given λ and M and the profile for D 2(τ) becomes progressively flatter with increase in ω. Finally the axial distribution of the average concentration θ m of the solute over the channel cross-section is determined at different instants after the solute injection for several values of M, λ and ω. The present study is likely to have important bearing on the problem of dispersion of tracers in blood flow through arteries. 相似文献
979.
We prove that directly reducible lattices and selfdual subdirectly irreducible lattices of locally finite length are determined by their sublattice-lattices. As a corollary we obtain that splitting varieties are closed under the isomorphism of sublattice-lattices iff they are selfdual. A class of selfdual non-closed varieties is given too. 相似文献
980.
We consider a particular case of the matrix Carleman problem for two pairs of functions in a ring and find a constructive
solution of this problem. In addition, we propose an algorithm for the construction of solutions for two infinite systems
of smooth transition and for a system of two singular equations of special type.
Translated from Ukrainskii Matematicheskii Zhurnal, Vol. 49, No. 5, pp. 662–671, May, 1997 相似文献